How to retrieve list of songs from device using recycler adapter over a fragment in android

Question

I want to retrieve list of songs on a device using recycler adapter over Song Fragment. Content resolver implemented to retrieve list of songs is getting error. Please help

This is what i have done.

• I have created Song model
• Extended 3 fragments(Below is one of Song Fragment) from Main activity

My SongFragment

public class TabSong extends Fragment {
RecyclerView recyclerView;
RecyclerAdapter adapter;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Get the view from fragmenttab1.xml
    View v = inflater.inflate(R.layout.tab_song, container, false);
    recyclerView = (RecyclerView) v.findViewById(R.id.recycler_view);

    RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getActivity());
    recyclerView.setLayoutManager(mLayoutManager);

    adapter = new RecyclerAdapter();
    SongList();
    recyclerView.setAdapter(adapter);

    return v;
}

public void SongList() {
    String selection = MediaStore.Audio.Media.IS_MUSIC + " != 0";
    String sortOrder = MediaStore.Audio.Media.TITLE + " ASC";

    ContentResolver cr = getActivity().getContentResolver();
    String[] projection = {
            MediaStore.Audio.Media._ID,
            MediaStore.Audio.Media.ARTIST,
            MediaStore.Audio.Media.TITLE,
            MediaStore.Audio.Media.DATA,
            MediaStore.Audio.Media.DISPLAY_NAME,
            MediaStore.Audio.Media.DURATION
    };

    Cursor cur = cr.query(
            MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
            projection,
            selection,
            null,
            sortOrder);

    RecyclerAdapter.songs = new ArrayList<>();
    while (cur.moveToNext()) {
        HashMap<String, String> map = new HashMap<>();
  /*  songs.add(cur.getString(0) + "||"
            + cur.getString(1) + "||"
            + cur.getString(2) + "||"
            + cur.getString(3) + "||"
            + cur.getString(4) + "||" );*/

        map.put("ID", cur.getString(0));
        map.put("artist", cur.getString(1));
        map.put("title", cur.getString(2));
        map.put("displayname", cur.getString(3));
        map.put("duration", cur.getString(4));

        RecyclerAdapter.songs.add(map);
    }
}}

My RecyclerAdapter

public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.MyViewHolder>{ 

static ArrayList<HashMap<String, String>> songs = new ArrayList<>();

@Override
public RecyclerAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.song_list, parent, false);
    MyViewHolder holder = new MyViewHolder(view);
    return holder;
}

@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
    holder.title.setText(songs.get(position).get("displayname"));
    holder.artist.setText(songs.get(position).get("artist"));
    holder.duration.setText(songs.get(position).get("duration"));
}

@Override
public int getItemCount() {
    return songs.size();
}

public class MyViewHolder extends RecyclerView.ViewHolder{
    public TextView title,duration,artist;

    public MyViewHolder(View view) {
        super(view);
        title = (TextView) view.findViewById(R.id.list_title);
        artist = (TextView) view.findViewById(R.id.list_artist);
        duration = (TextView) view.findViewById(R.id.list_duration);
    }
}}

Answer 1

#1: Don't use a static member to store songs in the adapter. All you need is a List of some class that you can define to hold all your song data.

public class Song {
    String displayName;
    String artist;
    // etc.
}

Make a method in your adapter to swap in the new List whenever it gets loaded. Speaking of which...

#2: You should be using a Loader to load the songs. There is a guide on Loaders here. The way you do it now is querying the MediaProvider on the UI thread and processing the result also on the UI thread, which is bad. Also, Loaders can automatically reload if the data changes, which means you don't have to manually refresh.

You can use a basic CursorLoader to start, although you would still be processing the results on the main thread inside of onLoadFinished(). If you want to do this better, you can make a custom Loader that does the query and also processes the result all in the background, and then publishes the final data structure.

Also, make sure you close the Cursor when you are done with it.

#3: After you add, remove, or change items backing your adapter, you need to call one of the notify... methods on the adapter (see the docs starting here) so that RecyclerView will show the updated data.